Benchtop Zone Refinement of Simulated Future Spent Nuclear Fuel Pyroprocessing Waste.

The UK's adoption of pyroprocessing of spent nuclear fuel as an alternative to the current aqueous processing routes requires a robust scientific underpinning of all relevant processes. One key process is the clean-up of the contaminated salt from the electroreducing and electrorefining processes. A proposed method for this clean-up is zone refining, whereby the tendency of the contaminants to remain in the liquid phase during melting and freezing is exploited to 'sweep' the contaminants to one end of the sample. Experiments were performed, utilising off-the-shelf laboratory equipment, to demonstrate the feasibility of zone refining for clean-up of electroreducing and electrorefining wastes. This was successful for the electrorefining simulant samples, with effective segregation coefficient, keff, values, which provide a measure of the degree of separation in the sample, between 0 and 1. Lower values indicate greater separation, with values of as low as 0.542 achieved here, corresponding to a reduction in RECl3 content from 10.0 wt.% to 8.4 wt.% (for 80% salt reuse). Due to difficulties in obtaining a fully homogeneous electroreducing simulant waste, it was not possible to demonstrate the feasibility of zone refining using the current experimental setup. Further research is required to elucidate the correct preparation conditions for production of homogeneous electroreducing waste simulants.

Antimicrobial Fe2O3-CuO-P2O5 glasses.

Glasses with high antimicrobial efficacy were developed in the Fe2O3-CuO-P2O5 ternary system to mitigate fomite-mediated transmission of infectious diseases in high-risk settings such as hospitals, daycares, and nursing homes. Binary CuO-P2O5 glasses were not durable enough for use as high touch point articles, so Fe2O3 was added to the compositions to increase the chemical durability. The amount of Cu leachate decreased by at least 3 orders of magnitude when Fe2O3 was increased from 0 to 13.1 mol%. At the highest Fe2O3 contents and corresponding highest durability, the glass was no longer able to pass a test of antimicrobial efficacy with < 3 log kill compared to > 5 log kill for all other compositions. Ab-initio molecular dynamics simulations showed increasing bridging oxygen species at the expense of non-bridging oxygen species with the increase in Fe2O3 content, showing that the glasses exhibited increased chemical durability because they were more interconnected and structurally bound. Experimental results with glasses at fixed CuO and decreasing Fe2O3 confirmed that Fe2O3 content (not CuO) controlled the Cu release rate and, thus, the antimicrobial efficacy of the glasses. The significance of the oxidation state of the leached Cu was overwhelmed by the importance of the amount of Cu leachate.

Effects of iron substitution and anti-site disorder on crystal structures, vibrational, optical and magnetic properties of double perovskites Sr2(Fe1-xNix)TeO6.

The double-perovskite series, Sr2(Fe1-xNix)TeO6 (x = 0, 0.25, 0.50, 0.75, and 1) has been synthesized in polycrystalline form by solid-state reaction at 1300 K in air. Their crystal structures were probed by powder X-ray diffraction at room temperature. Rietveld analysis revealed that all samples crystallize in the monoclinic space group I2/m. The double-perovskite structures ideally contain two alternating types of octahedra (Fe/Ni)2dO6 and (Te)2aO6, tilted in the system (a-a-c0). However, the refinements have shown a complex distribution of all three cations over the two available octahedral sites; 2d (½, ½, 0) and 2a (0, 0, 0). Raman spectroscopy further complements the obtained results, by revealing a tiny increase of the wavenumber of some Raman modes when Fe is substituted by Ni. The optical characteristics of the series were determined by fitting diffuse reflectance UV/Vis spectra enabling the optical band gaps to be derived from Tauc method and derivation of absorption spectra fitting (DASF) techniques. Analyses of the obtained 57Fe Mössbauer hyperfine parameters at room temperature of samples with compositions x = 0, 0.25, 0.50 and 0.75 reveal the presence of Fe3+ in high-spin state with an anti-site disorder of Fe-Ni-Te cations in distorted octahedral environments (site 2d and 2a). The results show that significant correlations exist between the crystal structures and physical properties of double perovskites containing B site transition elements of different charge and size. Temperature-dependent magnetic susceptibility data show magnetic transitions below 40(1) K (38(1) K, 31(1) K, 25(1) K, 20(1) K, and 35(1) K for x = 0, 0.25, 0.50, 0.75, and 1, respectively. A divergence between FC and ZFC curves for all compositions has been observed. The results show that the ground states of the doped materials might be spin glasses or magnetically ordered.

Elucidating the Mechanistic Origin of a Spin State-Dependent FeNx-C Catalyst toward Organic Contaminant Oxidation via Peroxymonosulfate Activation.

Atomically dispersed metals on nitrogen-doped carbon matrices have attracted extensive interest in the removal of refractory organic pollutants. However, a thorough exploration of the particular structure for each active site and specific effects of these sites still remains elusive. Herein, an Fe-pyridinic N4 structure in a single-atom catalyst (FeNx-C) was constructed using a facile pyrolysis strategy, and it exhibited superior catalytic activity in peroxymonosulfate (PMS) activation toward organic contaminant oxidation. The various Fe species and relative amounts of each Fe site in the FeNx-C catalyst were validated using X-ray absorption spectroscopy and 57Fe Mössbauer spectroscopy, which showed critical dependencies on the precursor ratio and calcination temperature. The positive correlations between relative content of high-spin state species (FeII and FeIII) and catalytic performance were found to determine the reactive species generation and electron transfer pathway in the FeNx-C/PMS system. Moreover, catalytic performance and theoretical calculation results revealed that FeII-N4 in the high-spin state (S = 2) tends to activate PMS to form sulfate and hydroxyl radicals via a one-electron transfer process, while the FeIII-N4 moiety (S = 5/2) is prone to high-valent iron species generation with lower free energy. Benefiting from finely tuned active sites, a single-atom FeNx-C catalyst achieved favorable applicability in actual wastewater treatment with efficient resistance of the common water matrix. The present work advances the mechanistic understanding of spin state-dependent persulfate activation in single-atom catalysts and provides guidance to design a superior catalyst based on spin state descriptions.

Self-Assembly of Nanosheet-Supported Fe-MOF Heterocrystals as a Reusable Catalyst for Boosting Advanced Oxidation Performance via Radical and Nonradical Pathways.

Heterojunction catalysts have drawn increasing interest for the visible light-driven Fenton reaction and bring tremendous opportunities for environmental remediation. Herein, a BiOI/MIL-53(Fe) Z-scheme heterojunction (named BMFe) was synthesized for the first time via a facile strategy. Compared with pristine BiOI and MIL-53(Fe) catalysts, the two-dimensional/three-dimensional (2D/3D) heterojunction catalyst manifested remarkable catalytic performance toward degradation of phenol, bisphenol A, methylene blue, and carbamazepine, which is attributed mainly to the interfacial integration and efficient charge separation. By virtue of coupling at the interface, as confirmed by XPS, 57Fe Mössbauer spectroscopy, and DFT calculations, the BMFe catalyst promoted the transfer of electron-hole pairs via Z-scheme and improved the chemical activation of hydrogen peroxide. The subsequent holes, free radicals, and nonradicals can effectively and continuously decompose pollutants, achieving a positive synergistic effect between photocatalysis and Fenton reactions. Simultaneously, the specially designed BiOX(X = Br, Cl)/MIL-53(Fe) and BiOI/Fe-MOFs(MIL-101, MIL-88) heterojunctions also exhibited advanced oxidative capacity for organic pollutants. Given their practical value for industrial applications, BMFe beads (1.0 ± 0.15 mm) synthesized via a blend cross-linking method can significantly advance long-term stability and recyclability. The integration of Fe-based metal-organic frameworks with bismuth oxyhalide semiconductors provides a new perspective on developing heterojunction catalysts for environmental remediation.

BiOBr/MoS2 catalyst as heterogenous peroxymonosulfate activator toward organic pollutant removal: Energy band alignment and mechanism insight.

Utilization of heterogenous catalysts to trigger peroxymonosulfate (PMS) activation is considered an efficient strategy for environmental decontamination. Herein, a tightly bonded flake-like 2D/2D BiOBr/MoS2 heterojunction was successfully designed through co-precipitation process. By virtue of matched energy levels and intimate interfacial coupling, the Type-II BiOBr/MoS2 heterojunction significantly expedited charge carrier transfer and thereby promoted the catalytic performance for organic dye oxidation and Cr(VI) reduction. The specially designed BiOBr/MoS2 heterojunction is also conducive to split PMS and continuously generated highly active species (SO4-, OH and O2-) in a photo-Fenton system, achieving extraordinary catalytic capacity for various emerging organic pollutants (including phenol, bisphenol A and carbamazepine). The photoexcited electron with prolonged lifetime and exposed Mo sites with multivalence and multiphase nature can effectively activate PMS, which further promotes the oxidation efficiency of holes, as confirmed by scavenging experiments. The excellent stability and oxidative properties could justify scale up using BiOBr/MoS2 to a small pilot test, implementing the potential value in practical applications. This study would provide novel insight and cognition of PMS activation via a superior heterojunction for complex polluted wastewater treatment.

An injectable, self-healing and MMP-inhibiting hyaluronic acid gel via iron coordination.

Regulating the activity of matrix metalloproteinases (MMPs) is a potential strategy for osteoarthritis (OA) therapy, although delivering this effect in a spatially and temporally localised fashion remains a challenge. Here, we report an injectable and self-healing hydrogel enabling factor-free MMP regulation and biomechanical competence in situ. The hydrogel is realised within 1 min upon room temperature coordination between hyaluronic acid (HA) and a cell-friendly iron-glutathione complex in aqueous environment. The resultant gel displayed up to 300% in shear strain and tolerance towards ATDC 5 chondrocytes, in line with the elasticity and biocompatibility requirements for connective tissue application. Significantly enhanced inhibition of MMP-13 activity was achieved after 12 h in vitro, compared with a commercial HA injection (OSTENIL® PLUS). Noteworthy, 24-hour incubation of a clinical synovial fluid sample collected from a late-stage OA patient with the reported hydrogel was still shown to downregulate synovial fluid MMP activity (100.0 ± 17.6% ➔ 81.0 ± 7.5%), with at least comparable extent to the case of the OSTENIL® PLUS-treated SF group (100.0 ± 17.6% ➔ 92.3 ± 27.3%). These results therefore open up new possibilities in the use of HA as both mechanically-competent hydrogel as well as a mediator of MMP regulation for OA therapy.

Structure and magnetism of the Rh4+-containing perovskite oxides La0.5Sr0.5Mn0.5Rh0.5O3 and La0.5Sr0.5Fe0.5Rh0.5O3.

Synchrotron X-ray powder diffraction data indicate that La0.5Sr0.5Mn0.5Rh0.5O3 and La0.5Sr0.5Fe0.5Rh0.5O3 adopt distorted perovskite structures (space group Pnma) with A-site and B-site cation disorder. A combination of XPS and 57Fe Mössbauer data indicate the transition metal cations in the two phases adopt Mn3+/Rh4+ and Fe3+/Rh4+ oxidation state combinations respectively. Transport data indicate both phases are insulating, with ρ vs. T dependences consistent with 3D variable-range hopping. Magnetisation data reveal that La0.5Sr0.5Mn0.5Rh0.5O3 adopts a ferromagnetic state below Tc ∼ 60 K, which is rationalized on the basis of coupling via a dynamic Jahn-Teller distortion mechanism. In contrast, magnetic data reveal La0.5Sr0.5Fe0.5Rh0.5O3 undergoes a transition to a spin-glass state at T ∼ 45 K, attributed to frustration between nearest-neighbour Fe-Rh and next-nearest-neighbour Fe-Fe couplings.

The facile and additive-free synthesis of a cell-friendly iron(iii)-glutathione complex.

The straightfoward creation of an unreported glutathione-stabilised iron(iii) complex is disclosed. In contrast to previous reports, glutathione was shown to coordinate and stabilise iron directly under physiological conditions in the absence of additional sulfur containing molecules, such as sodium sulfide. The complex was extensively characterised; the molecular geometry was determined as two inequivalent octahedra, approximately 2/3 of which are slightly distorted towards more tetrahedral in character, with the remaining 1/3 more regularly octahedral. The dispersion of the iron(iii)-glutathione complex in aqueous solution yielded particles of 255 ± 4 nm in diameter that enhanced the growth and proliferation of L929 fibroblast cells over 7 days, and inhibited the activity of matrix metalloproteinase-13. Consequently, the unprecedented glutathione-stabilised iron(iii) complex disclosed has potential use as a simple-to-prepare growth factor for inclusion within cell culture media, and is an excellent candidate as a therapeutic for the treatment of metalloproteinase-13-associated diseases.

Neutron Diffraction and Raman Studies of the Incorporation of Sulfate in Silicate Glasses.

The oxidation state, coordination, and local environment of sulfur in alkali silicate (R2O-SiO2; R = Na, Li) and alkali/alkaline-earth silicate (Na2O-MO-SiO2; M = Ca, Ba) glasses have been investigated using neutron diffraction and Raman spectroscopy. With analyses of both the individual total neutron correlation functions and suitable doped-undoped differences, the S-O bonds and (O-O)S correlations were clearly isolated from the other overlapping correlations due to Si-O and (O-O)Si distances in the SiO4 tetrahedra and the modifier-oxygen (R-O and M-O) distances. Clear evidence was obtained that the sulfur is present as SO4 2- groups, confirmed by the observation in the Raman spectra of the symmetric S-O stretch mode of SO4 2- groups. The modifier-oxygen bond length distributions were deconvoluted from the neutron correlation functions by fitting. The Na-O and Li-O bond length distributions were clearly asymmetric, whereas no evidence was obtained for asymmetry of the Ca-O and Ba-O distributions. A consideration of the bonding shows that the oxygen atoms in the SO4 2- groups do not participate in the silicate network and as such constitute a third type of oxygen, "non-network oxygen", in addition to the bridging and non-bridging oxygens that are bonded to silicon atoms. Thus, each individual sulfate group is surrounded by a shell of modifier and is not connected directly to the silicate network. The addition of SO3 to the glass leads to a conversion of oxygen atoms within the silicate network from non-bridging to bridging so that there is repolymerization of the silicate network. There is evidence that SO3 doping leads to changes in the form of the distribution of Na-O bond lengths with a reduction in the fitted short-bond coordination number and an increase in the fitted long-bond coordination number, and this is consistent with repolymerization of the silicate network. In contrast, there is no evidence that SO3 doping leads to a change in the distribution of Li-O bond lengths with a total Li-O coordination number consistently in excess of 4.

CO3+1 network formation in ultra-high pressure carbonate liquids.

Carbonate liquids are an important class of molten salts, not just for industrial applications, but also in geological processes. Carbonates are generally expected to be simple liquids, in terms of ionic interactions between the molecular carbonate anions and metal cations, and therefore relatively structureless compared to more "polymerized" silicate melts. But there is increasing evidence from phase relations, metal solubility, glass spectroscopy and simulations to suggest the emergence of carbonate "networks" at length scales longer than the component molecular anions. The stability of these emergent structures are known to be sensitive to temperature, but are also predicted to be favoured by pressure. This is important as a recent study suggests that subducted surface carbonate may melt near the Earth's transition zone (~44 km), representing a barrier to the deep carbon cycle depending on the buoyancy and viscosity of these liquids. In this study we demonstrate a major advance in our understanding of carbonate liquids by combining simulations and high pressure measurements on a carbonate glass, (K2CO3-MgCO3) to pressures in excess of 40 GPa, far higher than any previous in situ study. We show the clear formation of extended low-dimensional carbonate networks of close CO32- pairs and the emergence of a "three plus one" local coordination environment, producing an unexpected increase in viscosity with pressure. Although carbonate melts may still be buoyant in the lower mantle, an increased viscosity by at least three orders of magnitude will restrict the upward mobility, possibly resulting in entrainment by the down-going slab.

Structure and properties of Na5FeSi4O12 crystallized from 5Na2O-Fe2O3-8SiO2 glass.

The phase Na5FeSi4O12 [pentasodium iron(III) silicate] crystallizes readily from the Na2O-Fe2O3-SiO2 glass system in a relatively large compositional range. However, its crystal structure and properties have not been studied in detail since its discovery in 1930. In this work, the Na5FeSi4O12 phase was crystallized from a host glass with 5Na2O·Fe2O3·8SiO2 stoichiometry, and both the glass and the crystal were studied. It was found that the Na5FeSi4O12 phase crystallizes at ∼720 °C from the glass and melts at ∼830 °C when heated at a rate of 10 °C min-1. The crystal structure was solved using single-crystal X-ray diffraction and the refined data are reported for the first time for the Na5FeSi4O12 phase. It exhibits trigonal symmetry, space group R-3c, with a = 21.418 and c = 12.2911 Å. The Na atoms located between adjacent structural channels exhibit positional disorder and splitting which was only refined by using low-temperature data collection (150 K). While ∼7% of the total Fe cations occur as Fe2+ in the glass, four-coordinated Fe3+ constitutes ∼93% of the total Fe cations. However, iron in the crystal, which exhibits a paramagnetic behavior, is solely present as six-coordinated Fe3+. The magnetic and vibrational properties of the glass and crystal are discussed to provide additional insight into the structure.

Complex Magnetic Ordering in the Oxide Selenide Sr2Fe3Se2O3.

Sr2Fe3Se2O3 is a localized-moment iron oxide selenide in which two unusual coordinations for Fe2+ ions form two sublattices in a 2:1 ratio. In the paramagnetic region at room temperature, the compound adopts the crystal structure first reported for Sr2Co3S2O3, crystallizing in space group Pbam with a = 7.8121 Å, b = 10.2375 Å, c = 3.9939 Å, and Z = 2. The sublattice occupied by two-thirds of the iron ions (Fe2 site) is formed by a network of distorted mer-[FeSe3O3] octahedra linked via shared Se2 edges and O vertices forming layers, which connect to other layers by shared Se vertices. As shown by magnetometry, neutron powder diffraction, and Mössbauer spectroscopy measurements, these moments undergo long-range magnetic ordering below TN1 = 118 K, initially adopting a magnetic structure with a propagation vector (1/2 - δ, 0, 1/2) (0 ≤ δ ≤ 0.1) which is incommensurate with the nuclear structure and described in the Pbam1 '( a01/2)000 s magnetic superspace group, until at 92 K ( TINC) there is a first order lock-in transition to a structure in which these Fe2 moments form a magnetic structure with a propagation vector (1/2, 0, 1/2) which may be modeled using a 2 a × b × 2 c expansion of the nuclear cell in space group 36.178 B a b21 m (BNS notation). Below TN2 = 52 K the remaining third of the Fe2+ moments (Fe1 site) which are in a compressed trans-[FeSe4O2] octahedral environment undergo long-range ordering, as is evident from the magnetometry, the Mössbauer spectra, and the appearance of new magnetic Bragg peaks in the neutron diffractograms. The ordering of the second set of moments on the Fe1 sites results in a slight reorientation of the majority moments on the Fe2 sites. The magnetic structure at 1.5 K is described by a 2 a × 2 b × 2 c expansion of the nuclear cell in space group 9.40 I a b (BNS notation).

Doped Sr2FeIrO6-Phase Separation and a Jeff ≠ 0 State for Ir5.

High-resolution synchrotron X-ray and neutron powder diffraction data demonstrate that, in contrast to recent reports, Sr2FeIrO6 adopts an I1̅ symmetry double perovskite structure with an a-b-c- tilting distortion. This distorted structure does not tolerate cation substitution, with low levels of A-site (Ca, Ba, La) or Fe-site (Ga) substitution leading to separation into two phases: a stoichiometric I1̅ phase and a cation-substituted, P21/ n symmetry, a-a-c+ distorted double perovskite phase. Magnetization, neutron diffraction, and 57Fe Mössbauer data show that, in common with Sr2FeIrO6, the cation substituted Sr2- xA xFe1- yGa yIrO6 phases undergo transitions to type-II antiferromagnetically ordered states at TN ∼ 120 K. However, in contrast to stoichiometric Sr2FeIrO6, cation substituted samples exhibit a further magnetic transition at TA ∼ 220 K, which corresponds to the ordering of Jeff ≠ 0 Ir5+ centers in the cation-substituted, P21/ n symmetry, double perovskite phases.

Integrated management of ash from industrial and domestic combustion: a new sustainable approach for reducing greenhouse gas emissions from energy conversion.

This work supports, for the first time, the integrated management of waste materials arising from industrial processes (fly ash from municipal solid waste incineration and coal fly ash), agriculture (rice husk ash), and domestic activities (ash from wood biomass burning in domestic stoves). The main novelty of the paper is the reuse of wood pellet ash, an underestimated environmental problem, by the application of a new technology (COSMOS-RICE) that already involves the reuse of fly ashes from industrial and agricultural origins. The reaction mechanism involves carbonation: this occurs at room temperature and promotes permanent carbon dioxide sequestration. The obtained samples were characterized using XRD and TGA (coupled with mass spectroscopy). This allowed quantification of the mass loss attributed to different calcium carbonate phases. In particular, samples stabilized using wood pellet ash show a weight loss, attributed to the decomposition of carbonates greater than 20%. In view of these results, it is possible to conclude that there are several environmental benefits from wood pellet ash reuse in this way. In particular, using this technology, it is shown that for wood pellet biomass the carbon dioxide conversion can be considered negative.

Magnetic interactions in cubic-, hexagonal- and trigonal-barium iron oxide fluoride, BaFeO2F.

(57)Fe Mössbauer spectra have been recorded from the hexagonal (6H)- and trigonal (15R)- modifications of BaFeO2F and are compared with those previously recorded from the cubic form of BaFeO2F. The spectra, recorded over a temperature range from 15 to 650 K show that all of the iron in all the compounds is in the Fe(3+) state. Spectra from the 6H- and 15R-modifications were successfully fitted with components that were related to the Fe(1) and Fe(2) structural sites in the 6H variant and to the Fe(1), Fe(2) and Fe(3) structural sites in the 15R form. The magnetic ordering temperatures were determined as 597 ± 3 K for 6H-BaFeO2F and 636 ± 3 K for 15R-BaFeO2F. These values are surprisingly close to the value of 645 ± 5 K determined for the cubic form. The magnetic interactions in the three forms are compared with a view to explaining this similarity of magnetic ordering temperature.

Synthesis and characterisation of Li11RE18M4O39-δ: RE = Nd or Sm; M = Al, Co or Fe.

Four new phases of general formula, Li11RE18M4O39-δ: REM = NdAl, NdCo, SmCo, SmFe, have been synthesised and characterised. The NdAl phase, and probably the others, is isostructural with the NdFe analogue, but some cation disorder and partial site occupancies prevent full structural refinement of powder neutron diffraction data. The NdCo phase also forms a solid solution with variable Li content (and charge compensation by either oxygen vacancies or variable transition metal oxidation state). The NdAl phase is a modest conductor of Li(+) ions whereas the other three phases are electronic conductors, attributed to mixed valence of the transition metal ions. Subsolidus phase diagrams for the systems Li2O-Nd2O3-Al2O3, 'CoO' have been determined and an additional new phase, LiCoNd4O8, which appears to have a K2NiF4-related superstructure, identified.

Soft chemical control of superconductivity in lithium iron selenide hydroxides Li(1-x)Fe(x)(OH)Fe(1-y)Se.

Hydrothermal synthesis is described of layered lithium iron selenide hydroxides Li(1-x)Fe(x)(OH)Fe(1-y)Se (x ∼ 0.2; 0.02 < y < 0.15) with a wide range of iron site vacancy concentrations in the iron selenide layers. This iron vacancy concentration is revealed as the only significant compositional variable and as the key parameter controlling the crystal structure and the electronic properties. Single crystal X-ray diffraction, neutron powder diffraction, and X-ray absorption spectroscopy measurements are used to demonstrate that superconductivity at temperatures as high as 40 K is observed in the hydrothermally synthesized samples when the iron vacancy concentration is low (y < 0.05) and when the iron oxidation state is reduced slightly below +2, while samples with a higher vacancy concentration and a correspondingly higher iron oxidation state are not superconducting. The importance of combining a low iron oxidation state with a low vacancy concentration in the iron selenide layers is emphasized by the demonstration that reductive postsynthetic lithiation of the samples turns on superconductivity with critical temperatures exceeding 40 K by displacing iron atoms from the Li(1-x)Fe(x)(OH) reservoir layer to fill vacancies in the selenide layer.

Topochemical reduction of the Ruddlesden-Popper phases Sr2Fe(0.5)Ru(0.5)O4 and Sr3(Fe(0.5)Ru(0.5))2O7.

Reaction of the Ruddlesden-Popper phases Sr2Fe(0.5)Ru(0.5)O4 and Sr3(Fe(0.5)Ru(0.5))2O7 with CaH2 results in the topochemical deintercalation of oxide ions from these materials and the formation of samples with average compositions of Sr2Fe(0.5)Ru(0.5)O(3.35) and Sr3(Fe(0.5)Ru(0.5))2O(5.68), respectively. Diffraction data reveal that both the n = 1 and n = 2 samples consist of two-phase mixtures of reduced phases with subtly different oxygen contents. The separation of samples into two phases upon reduction is discussed on the basis of a short-range inhomogeneous distribution of iron and ruthenium in the starting materials. X-ray absorption data and Mössbauer spectra reveal the reduced samples contain an Fe(3+) and Ru(2+/3+) oxidation state combination, which is unexpected considering the Fe(3+)/Fe(2+) and Ru(3+)/Ru(2+) redox potentials, suggesting that the local coordination geometry of the transition metal sites helps to stabilize the Ru(2+) centers. Fitted Mössbauer spectra of both the n = 1 and n = 2 samples are consistent with the presence of Fe(3+) cations in square planar coordination sites. Magnetization data of both materials are consistent with spin glass-like behavior.

Topochemical fluorination of Sr3(M(0.5)Ru(0.5))2O7 (M = Ti, Mn, Fe), n = 2, Ruddlesden-Popper phases.

Reaction of the appropriate Sr3(M(0.5)Ru(0.5))2O7 (M = Ti, Mn, Fe), n = 2, Ruddlesden-Popper oxide with CuF2 under flowing oxygen results in formation of the oxide-fluoride phases Sr3(Ti(0.5)Ru(0.5))2O7F2, Sr3(Mn(0.5)Ru(0.5))2O7F2, and Sr3(Fe(0.5)Ru(0.5))2O(5.5)F(3.5) via a topochemical anion insertion/substitution process. Analysis indicates the titanium and manganese phases have Ti(4+), Ru(6+) and Mn(4+), Ru(6+) oxidation state combinations, respectively, while Mössbauer spectra indicate an Fe(3+), Ru(5.5+) combination for the iron phase. Thus, it can be seen that the soft fluorination conditions employed lead to formation of highly oxidized Ru(6+) centers in all three oxide-fluoride phases, while oxidation states of the other transition metal M cations remain unchanged. Fluorination of Sr3(Ti(0.5)Ru(0.5))2O7 to Sr3(Ti(0.5)Ru(0.5))2O7F2 leads to suppression of magnetic order as the fluorinated material approaches metallic behavior. In contrast, fluorination of Sr3(Mn(0.5)Ru(0.5))2O7 and Sr3(Fe(0.5)Ru(0.5))2O7 lifts the magnetic frustration present in the oxide phases, resulting in observation of long-range antiferromagnetic order at low temperature in Sr3(Mn(0.5)Ru(0.5))2O7F2 and Sr3(Fe(0.5)Ru(0.5))2O(5.5)F(3.5). The influence of the topochemical fluorination on the magnetic behavior of the Sr3(M(0.5)Ru(0.5))2O(x)F(y) phases is discussed on the basis of changes to the ruthenium oxidation state and structural distortions.